Bevel gear unit

ABSTRACT

Provided is a bevel gear unit with continuous gearing adjustment, for which the contact pressure between the bevel gear pairs and the traction means is generated hydraulically on one gear unit side and mechanically, with the aid of a spring, on the other gear unit side. For this, the second gear unit side is provided with an axially fixed bevel gear and an axially movable bevel gear with extended hub, wherein the bevel gears are connected so as to rotate jointly on their gear unit shaft and are coupled to the shaft via a contact pressure mechanism that depends on the rotational moment or a rotational moment and the gearing. The contact pressure mechanism consists of a cam sleeve that is fixed relative to the shaft, a cam sleeve formed by the free end of the hub and roll bodies for the force transmittal, which are inserted between opposite arranged cam curves and rotate around axes extending radial to the gear unit shaft. The roll bodies are guided by rings and are held at a mutual distance to each other and with spring force in the axial center region between the cam sleeves, wherein the spring is arranged coaxial on the extended hub.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority of German Patent ApplicationSerial No. 100 58 475.6 filed on Nov. 24, 2000, the subject matter ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a bevel gear unit withcontinuous adjustment of the gearing and generating of axial contactpressures exerted by the bevel gears onto a traction means, rotatingbetween these bevel gears, via tensioning means arranged on the gearunit shafts, which act in axial direction onto respectively one bevelgear that can be axially displaced along the respective gear unit shaft.For this, hydraulic means are provided on a first gear unit side foradjusting and maintaining the gearing and a spring that is bracedagainst a support, fixed relative to the shaft, is provided on thesecond gear unit side.

[0003] A bevel gear unit of this type is known, among other things, fromGerman reference DE 43 00 879 and is used whenever a cost-effective gearunit is desired for small vehicles and simple industrial applications.The disadvantage of the known gear unit, however, is its inability togenerate load-dependent contact pressure forces between bevel gears andtraction means. Rather, the spring that generates the contact pressureforce on one of the gear unit sides determines the output limit for thegear unit. In other words, it means that the spring must be designed fora certain maximum output that can be transmitted by the gear unit. Witha low power transmission, the gear unit therefore operates with anexcess contact pressure between bevel gears and traction means and thuswith a more or less high loss.

[0004] In order to generate the above-mentioned contact pressure forcesload-dependent and with the lowest possible losses, it is known thatthese contact pressure forces can be generated with correspondingcontrol and exclusively with hydraulic means on both gear unit sides.Another option is to generate the contact pressure forces purelymechanical, with the aid of so-called contact pressure mechanisms.

[0005] A third option consists in the combination of these two systems,for example as disclosed by the subject matter of German references 2016 181 and 2 058 399. According to the aforementioned reference, thecontact pressure forces on both gear unit sides are generatedload-dependent with contact pressure mechanisms of the aforementionedtype. These mechanisms are parallel connected to a device for generatinghydraulic contact pressure forces for adjusting and maintaining the gearunit gearing. With respect to the design, it means that the respectiveaxially displaceable cam sleeve of the contact pressure mechanism isalso positioned axially displaceable on a neck-type extension of thebevel gear, which can be displaced in axial direction to vary the gearunit gearing, and is stressed in the direction toward the contactpressure mechanism cam sleeve that is fixed relative to the shaft by acompression spring, arranged between displaceable cam sleeve andadjacent bevel gear. This type of design is extremely space consuming,especially in radial direction, and is thus too costly for simple bevelgear units, especially when considering the scope of the hydrauliccontrol required to adjust and maintain the gear unit gearing.

[0006] It is the object of the invention to develop a more effectivebevel gear unit of the aforementioned type, which has a mechanicaldevice for the load-dependent generating of contact pressure forces, butdoes not require additional space on the gear unit side in question,particularly in radial direction.

SUMMARY OF THE INVENTION

[0007] This object is solved according to the invention by arranging onthe second gear unit side one axially fixed bevel gear and one axiallymovable bevel gear that is provided with an extended hub. The object isfurther solved by connecting the bevel gears so as to rotate togetherand such that they rotate jointly on their gear shaft and are coupled tothis shaft via a contact pressure mechanism depending on the rotationalmoment or a rotational moment and the gearing. The object is furthermoresolved in that the contact pressure mechanism consists of a cam sleeve,fixed relative to the shaft, a cam sleeve formed by the free end of theextended hub, as well as roll bodies, which are inserted between theopposite-arranged cam tracks and rotate around axes that are positionedradial relative to the gear shaft, so as to transmit the forces. Theroll bodies are guided by rings, are held at a mutual distance to eachother and are adjusted in axial direction with spring force to remain inthe region of the axial center between the cam sleeves by a spring thatis arranged coaxial on the extended hub.

[0008] These measures according to the invention make it possible forthe gear unit side with mechanical generating of the contact pressureforces to generate these contact pressure forces load-dependent and thusonly within the scope required for the momentary output transmitted bythe gear unit. The purpose of the spring that is now connected parallelto the contact pressure mechanism is reduced to providing a basiccontact pressure in case the gear unit is idling and no contact pressureforce is generated by the contact pressure mechanism. The gear unit thuscan operate without specific losses.

[0009] Since the axially displaceable cam sleeve for the contactpressure mechanism is now integrated into the free end of the extendedhub of the associated bevel gear, a design results that requirescomparatively no additional space in radial direction. In particular, itis not necessary to arrange the axially displaceable cam sleeve of thecontact pressure mechanism as additional component radially outside ofthe extended hub of the axially displaceable bevel gear, as is necessaryfor the above-described case.

[0010] Since the axially displaceable cam sleeve of the contact pressuremechanism is now an integral component of the axially displaceable bevelgear, as mentioned before, it means that this cam sleeve always assumesonly an axial position that corresponds to the gearing-dependent axialposition of the displaceable bevel gear. In the event that no load isapplied to the gear unit, it would then be possible for the roll bodiesto assume a position at the bottom of the cam curves formed by the camsleeves. If a load is applied once more, a spinning of the cam sleevescould result, at least in those gearing positions of the gear unit wherethe bevel gears of the second gear unit side are positioned closetogether. To keep this from happening, the additional feature of theinvention ensures that the roll bodies are always kept in the region ofthe axial center between the cam sleeves, even in the case of anon-loaded gear unit, meaning an idling gear unit.

[0011] In a manner known per se, it has proven advantageous that thebevel gears of the second gear unit side are arranged on a hollow shaft,which is positioned so as to rotate on the gear unit shaft but cannot bedisplaced in axial direction. It is furthermore advantageous that theaxially fixed bevel gear is rigidly connected to the hollow shaft, theaxially displaceable bevel gear is connected rotatingly to the hollowshaft and the cam sleeve that is fixed relative to the shaft is arrangednext to the hollow shaft on the gear unit shaft, such that it rotatesalong and cannot be moved axially, at least not in the direction awayfrom the opposite arranged cam sleeve. The axially fixed bevel gear inthis case can form one piece with the hollow shaft.

[0012] One embodiment of the invention advantageously provides that theroll bodies, having pinions that project radially from the roll bodiestoward the gear unit shaft and are coaxial to their rotational axes,engage in corresponding recesses in the rings. For this, a holding ringthat is coaxial to the shaft can be arranged radial to the gear unitshaft inside or outside of the roll bodies, wherein the pinions of theroll bodies are positioned so as to rotate inside holding ring boresthat are positioned radial to the gear unit shaft.

[0013] According to one design, a guide ring in the form of ahollow-cylindrical sleeve can be arranged radial to the gear unit shaft,outside of the roll bodies, which encloses the roll bodies as well asthe extended hub. The guide ring can be arranged so as to bedisplaceable, but non-rotating relative to the hub, in axial directionalong the extended hub while outward projecting pinions on the rollbodies are positioned so as to rotate inside circumferential slots thatextend along a radial plane of the gear unit shaft. The axial width ofthese slots corresponds to the diameter of the pinions and the pinionsare furthermore held in the axial center region between the cam sleeves.The length of the circumferential slots in circumferential directioncorresponds at least to half the maximum mutual circumferential pathcovered by the cam sleeves for the contact pressure mechanism.Furthermore, the guide ring end facing the axially movable bevel gear isconnected to the spring in such a way that moving in the same direction,it also traverses essentially half the axial path of the movable bevelgear each time.

[0014] For this, the spring can be braced against the axiallydisplaceable bevel gear as well as against the cam sleeve that is fixedrelative to the shaft. In further detail, the arrangement can actuallybe a disk spring assembly, one half of which is essentially arranged onthe hub and the other half on the guide ring. The spring can be bracedagainst the cam sleeve via a hollow-cylindrical intermediate segmentthat encloses the guide ring, wherein the guide ring is caught betweenthe two halves of the disk spring assembly with a radially outwardpointing collar at the end.

[0015] To ensure that the guide ring and thus also the circumferentialslots remain in the position assigned to the cam curves for the camsleeve, the guide ring section located on the hub is advantageouslyprovided with at least one groove extending parallel to the gear unitshaft. A pin supported by the hub engages in this groove to preventrotation.

[0016] The above-described first design also ensures that the rollbodies are always held with spring action in the axial center betweenthe two cam sleeves of the contact pressure mechanism, even if no loadis applied to the gear unit. On the other hand, they can also moveunhindered to the degree necessary in circumferential direction alongwith the cam curves of the contact pressure mechanism because of theguide ring. This ensures that the roll bodies always engage in the camcurves, even if the gear unit is switched from the idle state back to aload condition.

[0017] The same result is achieved with a second embodiment of theinvention. With this embodiment, a guide ring is arranged radial to thegear unit shaft outside of the roll bodies, which takes the form of atleast one assembly of axially side-by-side arranged, ring-shapedcorrugated springs with reciprocating undulations in axial directionalong the circumference. The guide ring furthermore is captured in axialdirection between a collar supported by the hub and a rotating collarsupported by the cam sleeve, fixed relative to the shaft, and is held inthe axial center position relative to the contact pressure mechanism.Radially outward projecting pinions on the roll bodies furthermore arepositioned so as to rotate in the axial center region of this guidering. Thus, a design has been developed, which ensures the axial centerpositioning of the roll bodies between the cam sleeves of the contactpressure mechanism, independent of the spring that guarantees the basiccontact pressure of the axially displaceable bevel gear.

[0018] As modification of this solution, the guide ring can be provided,which is composed of two identical, axially side-by-side arrangedcorrugated spring assemblies, wherein the corrugated springs of eachassembly are braced against each other and are fixedly connected to eachother via undulation crest that face each other. The pinions on the rollbodies are positioned so as to rotate between the corrugated disk springassemblies. To achieve the latter, the holding ring is advantageouslyarranged outside of the roll bodies, between these and the guide ringcomposed of corrugated springs, and is provided with a rotating collarthat projects radially outward from its axial center and extends betweenthe corrugated spring assemblies. For this, the bores in the holdingring for the roll body pinions can also extend through the collar. If,according to another feature of the invention, the axial width of thecollar corresponds to the thickness of the roll body pinions, onlycircumferential sections of the collar remain between the pinions ofneighboring roll bodies, as seen in circumferential direction. Thisrepresents a particularly space-saving and weight-saving design.

[0019] The spring that ensures the basic contact force of the axiallydisplaceable bevel gear for this design can be arranged on the hub andcan be braced against the axially movable bevel gear as well as againstthe cam sleeve that is fixed relative to the shaft via an essentiallyhollow-cylindrical intermediate segment that extends past the guidering. Furthermore, the guide ring collar supported by the cam sleeve,which is fixed relative to the shaft, and the intermediate segment canbe combined to form one component.

[0020] A bevel gear unit of the type discussed herein requires that fora change in the gear unit gearing, which requires emptying the pressurecylinder arranged on the first gear unit side, the necessary axial forceis derived via the traction means from the contact pressure forceexerted upon the traction means on the second gear unit side. This forceis also sufficient for a rapid adjustment of the gear unit gearing ifthe gear unit operates under normal load conditions. However, if thegear unit is in the idle state or at a standstill, only the springensuring the basic contact pressure is active on the second gear unitside. However, the force exerted by this spring, which is furtherreduced during the movement to the first gear unit side as a result offrictional forces, is only sufficient for a relatively slow adjustmentof the gear unit gearing in the above-mentioned cases. Added to this isthe fact that the pressure medium that must be pushed out of thepressure cylinder must also pass by the correspondingly adjusted controlvalve while overcoming corresponding resistances.

[0021] According to a modified version of the invention, a reversingvalve is installed in the intake line for the pressure medium tocounteract this effect, which reversing valve can connect the pressurechamber to the pressure medium supply or the suction-in side of apressure medium pump. As a result of this measure, the pressure mediumat least can flow unhindered from the pressure cylinder. The crosssection for a discharge of this type without problems be dimensionedaccordingly large. It is also possible to suction the pressure mediumfrom the pressure cylinder, meaning the adjustment of the gear unitgearing is actively encouraged.

[0022] It is understood that the activation of the reversing valveoccurs based on the remaining marginal conditions of the gear unit, atleast for the aforementioned critical cases. For this, the controldevice for the control valve [pilot valve?] can be used to activate thereversing valve, wherein the determinants for the gear unit operationare supplied to this control. However, this also requires a specialactivation member that is triggered by the control. Another optiontherefore may be to activate the reversing valve with the aid of thepressure existing in the pressure medium intake line. Since thispressure exerted by the pressure medium is derived from the valveposition specified by the control, a corresponding determinant isautomatically provided for adjusting the reversing valve. However, thedeterminant for this design option is also obtained automatically if,during a pause in the gear unit operation, the gearing is to be changed,so as to require the emptying of the pressure cylinder. However, thiscan only be helpful for a rapid change in the gear unit gearing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] These and other features and advantages of the invention will befurther understood from the following detailed description of thepreferred embodiments with reference to the accompanying drawings inwhich:

[0024]FIG. 1 Shows a simplified view of a continuously adjustable bevelgear unit.

[0025]FIG. 2 Shows the enlarged sectional representation of the secondgear unit side shown in FIG. 1, with mechanical generating of thecontact pressure forces in a first operating position.

[0026]FIG. 3 Shows the subject matter according to FIG. 2, in adifferent operating position.

[0027]FIG. 4 Shows a view from above of the subject matter according toFIG. 3, shown as a partial sectional view along the sectional line IV-IVin FIG. 3.

[0028]FIG. 5 Shows a detail of the subject matter according to FIG. 4,in a sectional view.

[0029]FIG. 6 Shows the progression of the cam position of the contactpressure mechanism for FIG. 2.

[0030]FIG. 7 Shows the progression of the cam position of the contactpressure mechanism for a different gearing position.

[0031]FIG. 8 Shows a different structural design of the gear unit sidewith mechanical generating of the contact pressure forces.

[0032]FIG. 9 Shows the sectional view IX-IX from FIG. 8.

[0033]FIG. 10 Shows the sectional view X-X from FIG. 8.

[0034]FIG. 11 Shows a detail from FIG. 8, in an axial view, as well astwo sectional views that are offset relative to each other by 90°.

[0035] FIGS. 12 to 14 Show three modified versions of the hydrauliccontrol shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The continuously adjustable bevel gear unit shown in FIG. 1 iscontained inside a schematically indicated housing 1 and essentiallycomprises shafts 3 and 4 that rotate inside the housing 1 via thebearings 2. Arranged on these shafts are bevel gears 5 to 8, betweenwhich a traction means 9 circulates. Arrows 10, 11 illustrate that theshaft 3 is the drive shaft for the gear unit shown herein, meaning theunit connected to shaft 3 represents the first gear unit side. The shaft4, on the other hand, is the output shaft of the gear unit and the unitconnected thereto represents the second gear unit side.

[0037] The bevel gear 5 is arranged on the shaft 3, such that it rotatesalong and cannot be displaced axially and, for the present case, formsone piece together with the shaft 3. On the other hand, the bevel gear 6can be displaced axially along the shaft 3, but is connected to thisshaft so as to rotate along via a serration 12. The axial adjustment ofbevel gear 6 occurs with a pressure cylinder 14 that forms a pressurechamber 13 and comprises a piston 15, fixed relative to the shaft, acylinder jacket 16 supported by the bevel gear 6 and a cylinder bottomformed by the bevel gear 6 itself.

[0038] The pressure cylinder 14 is connected via a pressure line 17 to acontrol valve 18, which is connected via a line 19 to the pressure sideof a pump 20 that can suction in pressure medium from a supply container21. On the other side, the control valve 18 is connected via areturn-flow line 22 directly to the supply container 21.

[0039] Depending on the position of the control valve 18, pressuremedium supplied by the pump 20 is fed to the pressure chamber 13, orpressure medium can be discharged via the line 17 and the line 22 fromthe cylinder chamber 13. The position of control valve 18 that isassociated with this return flow is shown in FIG. 1.

[0040] The control valve 18 thus functions to adjust and maintain thegear unit gearing. For this, the control valve 18 is activated via aline 23 by a control unit 24, to which the necessary operating variablesare supplied. The following are entered as operating variables for thepresent case of a motor vehicle: a speed n₁, for example the enginespeed, a speed n₂, for example the driving speed, as well as the enginethrottle valve position α.

[0041] On shaft 4 of the second gear unit side, the bevel gears 7 and 8are arranged on a hollow shaft 25, which can rotate, but cannot bedisplaced in axial direction on this shaft 4. The bevel gear 8 isfixedly connected to the hollow shaft 25 while the bevel gear 7 can bedisplaced in axial direction along the hollow shaft 25 but is connectedto it non-rotating via an adjusting spring 26.

[0042] Mechanical means for generating the necessary contact-pressureforce, relative to the traction means 9, act upon the bevel gear 7.These means are explained with the aid of FIG. 2, which shows the secondgear unit side from one half of FIG. 1.

[0043]FIG. 2 shows that the bevel gear 7 has an extended hub 27, onwhich a disk spring assembly 28 is positioned concentrically, which isbraced against the radially outward projecting collar 30 of a cam sleeve31 via a hollow-cylindrical intermediate section 29. The cam sleeve issupported at least in axial direction on the shaft 4, starting with thebevel gear 7 and is otherwise rotatingly connected to the shaft 4 via anadjusting spring 32. The disk spring assembly 28 exerts an axial forceonto the bevel gear 7, which depends somewhat on the axial position ofthe bevel gear 7 but remains essentially the same. Thus, the forceexerted onto the traction mechanism 9, which is only indicated herein,is always present as basic contact pressure and prevents the tractionmeans 9 from slipping through, relative to the bevel gears.

[0044] On the side facing the cam sleeve 31, the extended hub of bevelgear 7 also forms a cam sleeve 33. Roll bodies 36 are inserted betweenthe opposite-arranged cam curves 34 or 35 of cam sleeves 31 or 33, whichroll bodies can rotate around the axes 37 that are positioned radial tothe shaft 4. For the positioning of these roll bodies 36, they areprovided with outward projecting pinions 38 and inward projectingpinions 39. Inside the roll bodies 36, a rotating holding ring 40 isarranged on the hollow shaft 25 and accommodates the pinions 39 inmatching bores 41. Outside of the roll bodies 36, the projecting pinions38 engage in the circumferential slots 42 of a guide ring 43. The guidering end facing the axially displaceable bevel gear 7 is clamped in witha radially outward projecting collar 44 at the longitudinal center ofthe spring assembly 28. The guide ring is rotationally connected to thehub 27 via at least one groove 46 that extends parallel to the axis 45of shaft 4 and a radial pin 47 of hub 27 that engages in this groove.

[0045] The appearance of this guide ring 43 is illustrated once morewith further detail in FIG. 5, which shows this guide ring as a radialsection. In addition, FIG. 5 shows opposite arranged circumferentialslots 42, which correspond to two opposite-arranged roll bodies 36.These slots extend across an arc that is smaller than 180° but is largeenough so that the roll bodies 36 can perform the operationally requiredmovements along the cam curves 34, 35 of the contact pressure mechanismformed by the roll bodies and the cam sleeves 31, 33.

[0046] The circumferential positions of cam curves 34, 35 are shown inFIG. 6 and correspond to FIG. 2. It must be stated here that the bevelgears 7, 8 in the representation according to FIG. 2 are at theirgreatest distance from each other, which corresponds to the maximumadjustment of the gear unit at output speeds that are too slow.Correspondingly, the cam curves 34, 35 that extend along thecircumference are also adjusted to the smallest possible distancerelative to each other, so that the roll bodies 36 make contact with thecam curves in the region of their respective cam bottom 48 or 49. If,subsequently, a rotational moment occurs between the cam sleeves 31 and33, the roll bodies 36 want to run up along the cam curves 34 or 35. Asa result, the force seeks to move apart the cam curves 31, 33 in axialdirection. Since the cam sleeve 31 is rigidly supported in axialdirection on the shaft 4, this expanding force if transmitted via thecam sleeve 33 and the hub 27 directly to the bevel gear 7, where itbecomes a contact pressure force exerted onto the traction means 9. Thisforce corresponds to the magnitude of the rotational moment that occursand must be transmitted and, corresponding to the inclination of camcurves 34, 35, also corresponds to the variable for the gearing positionof the gear unit.

[0047]FIGS. 3 and 4 show the subject matter according to FIG. 2 in thegearing position, for which the bevel gears 7, 8 are at the shortestpossible distance to each other in axial direction. This positioncorresponds to the gearing position where the gear unit is adjustedtoward the fastest possible output speeds and involves the cam curves34, 35 being at a correspondingly grater mutual distance in axialdirection, as can be seen in FIG. 7. The roll bodies 36 in this case fitflush against the cam curves in the end regions of cam curves 34, 35when a rotational moment is transmitted.

[0048] If, for example, the gear unit enters a no-load or idle conditionduring this gearing position, no transmittal of the rotational momentoccurs between the cam sleeves 31, 33, which keeps the roll bodies 36 inthe center region between the cam curves 34, 35. Rather, the angleposition of the cam sleeves 31, 33 is undetermined, relative to eachother. In that case, the roll bodies could also assume the positionshown with dashed line in FIG. 7, for example on the cam bottom 48 ofcam curve 34. If a rotational moment then occurs again between the camsleeves 31, 33, the cam curve 35 could move past the roll bodies 36 incircumferential direction, without coming in contact with these. Itmeans that the cam sleeve would spin without the possibility oftransmitting the rotational moment.

[0049] The same situation could occur with respect to FIG. 7 if the gearunit were subjected to a reversal in the rotational direction, meaningthe cam sleeve 33 would jump from the position shown on the top of FIG.7 to the position shown on the bottom of FIG. 7.

[0050] The previously described guide ring 43 is designed to counteractthis. Since this guide ring with its collar 44 is attached to the diskspring assembly 28, approximately at the longitudinal center inlengthwise direction, it partially also experiences the longitudinalchange of the disk spring assembly 28, caused by the axial movement ofthe bevel gear 7. As a result and through the engagement in thecircumferential slots 42, the roll bodies 36 are always held in theregion of the axial center between the cam curves 34, 35.

[0051] The progression in FIG. 7 again shows the length of thecircumferential slots 42, which must be sufficient for the roll bodies36 to traverse the maximum path in circumferential direction, visible inFIG. 7, to match both rotational directions of the gear unit.

[0052] Finally, with respect to FIGS. 3 and 4, it must be pointed outthat differing from FIG. 7, the cam sleeves 31, 33 are shown in thecircumferential position relative to each other, for which the completecircumference of both opposite-arranged cam curves 34, 35 is shown. Sucha position is also conceivable for the no-load operation of the gearunit. It shows particularly clearly which degree of freedom of movementthe roll bodies 36 would have in axial direction of the shaft 4 if theywere not held by the guide ring 43 and its circumferential slots 42 inthe center between the two cam curves 34 and 35.

[0053] FIGS. 8 to 11 show a modified version of the design for thesecond ear unit side, illustrated in FIGS. 1 to 7, wherein the samesubjects are given the previously introduced reference numbers. It mustbe pointed out in this connection that FIG. 8 in the lower half of therepresentation shows the distance between the bevel gears 7, 8 accordingto FIG. 2 and in the upper half of the representation shows the distancebetween these bevel gears according to FIG. 3.

[0054]FIGS. 8 and 10 show the roll bodies 50 provided with only oneradially outward projecting rotating pinion 51, whereas in radial inwarddirection, the roll bodies are supported directly on the hollow shaft52, which in this case forms one piece with the bevel gear 8. The bevelgear 7 in turn is secured by means of a serration 53 on this hollowshaft, such that it can be moved in axial direction but is preventedfrom turning.

[0055] The pinions 51 extend through matching bores in a holding ring54, arranged radially outside of the roll bodies 50, and furthermoreproject into a guide ring 55 that is arranged outside of the holdingring 54 and consists of two corrugated spring assemblies 56, arrangedside-by-side in axial direction, as can be seen best in FIG. 10. Thesecorrugated springs 56, which extend circular around the circumference,are arranged relative to each other so as to fit against each other withfacing undulation crests 57, 58, which are connected non-detachable, forexample by welding them together.

[0056] The pinions 51 of roll bodies 50 project between the corrugatedspring assemblies. The holding ring 54 is provided with a radiallyoutward projecting collar 59 that engages between the corrugated springassemblies to keep the pinions together with the holding ring 54positioned in the center between the corrugated spring assemblies, ascan be seen in FIG. 11. The axial thickness of collar 59 corresponds inthis case to the diameter for pinion 51, so that the radially outwardcontinued bores 60 of holding ring 54 divide the collar 59 for thepinions 51.

[0057] The corrugated spring assemblies 55 are braced on the outside inaxial direction on one side against a collar 61, which is supported bythe free end of hub 27 or the cam sleeve 33 formed thereon. On the otherside, the corrugated spring assemblies are braced axially against acollar 62, attached in radial direction to the outside of cam sleeve 31.

[0058] An essentially hollow-cylindrical intermediate segment 63, whichaxially encircles the guide ring 55, is provided so that the axialcounter support for the disk spring assembly 28 also occurs via the camsleeve 31 that is fixed relative to the shaft, as previously describedfor the design shown in FIGS. 1 to 7. For reasons of simplicity, thisintermediate segment forms one unit with the collar 62 for the presentembodiment.

[0059] Corresponding to the two axial distances between the bevel gears7 and 8, shown in FIG. 8, the guide ring 55 of corrugated springs 56 isaxially compressed to form a block in the lower half of FIG. 8, whichalso includes the view according in FIG. 9. In contrast, the guide ringshown in the upper view of FIG. 8, which also includes FIG. 10, isexpanded to the maximum axial extent. As can be seen, it is alwaysensured that the roll bodies 50 are held in the axial center between thecam sleeves 31, 33, so that a spinning of the contact pressure mechanismthat comprises the cam sleeves cannot occur in the manner described withFIG. 7.

[0060] With the design for the second gear unit side, described indetail in the above with the aid of FIGS. 2 to 11, a variable thatdepends on the rotational moment and the gearing can be generated forthe contact pressure forces exerted onto the traction means 9. To returnto the view according to FIG. 1, this results in a correspondingexpansion force for the first gear unit side, with which the tractionmeans 9 attempts to push apart bevel gears 5 and 6 in axial direction.To counter this force and maintain and adjust the gearing, acorresponding pressure is generated inside the pressure chamber 13 ofpressure cylinder 14 by supplying a pressure medium via the controlvalve 18.

[0061] If, in particular during the standstill or idling of the gearunit, a change must be made in the gear unit gearing and it becomesnecessary to empty the pressure chamber 13, only the force of spring 28is available for pushing the pressure medium from the pressure chamber13. This spring force acts upon the axially displaceable bevel gear 7 onthe second gear unit side and attempts to displace the bevel gear 7 inaxial direction toward the bevel gear 8 via the traction means 9. As aresult, the bevel gear 6 is moved in axial direction away from the bevelgear 5. However, since only one basic variable exists for the spring 28force to ensure that the traction means does not hang down looselybetween the respective bevel gear pairs, it would take a correspondinglylong time to empty the pressure chamber 13 via the control valve 18 andthe return flow line 22, which frequently is not available or isundesirable.

[0062] To counteract this effect, a reversing valve 65 is arrangedinside the pressure medium line 17, wherein the reversing valve can beactuated by the control unit 24 via the line connection 66.

[0063] In the position shown in FIG. 1, the reversing valve 65 allowsthe hydraulic pressure, exerted by the control valve 18 onto thepressure line 17, to enter the pressure chamber 13 unhindered, whichrepresents a normal mode of operation for the gear unit.

[0064] However, if the previously described necessity for a gear unitadjustment during the standstill or idling occurs, which also involvescorresponding input variables for the control unit 24, then the controlunit 24 effects an adjustment of the reversing valve 65 to the otherposition shown in the drawing. As a result, the pressure chamber 13 isconnected to a return flow line 67, which empties directly into thepressure medium supply container 21. The return flow line 67 withoutproblems can have a large cross-sectional dimension, so that thepressure medium encounters practically no resistance during thedischarge from the pressure chamber 13. In this way, it is possible toempty the pressure chamber 13 relatively quickly to change the gear unitgearing, even if only the force of spring 28 is available. Theflow-through resistance of the control valve 18, also shown in thedischarge position in FIG. 1, is thus bridged.

[0065]FIG. 12 shows a variant for this embodiment, described with theaid of FIG. 1. All components previously explained with the aid of FIG.1 are given the same reference numbers and are not described again.

[0066] According to FIG. 12, the return flow line 68 of the reversingvalve 65 is connected to the suction-in side 69 of a pump 70, which hasa relatively low capacity because it generally is only used via apressure line 71 for oiling the traction means 9. For the gear unitadjustment in question, the connection between the pressure chamber 13and the suction-in side of pump 70 nevertheless leads to a furtherincrease in the discharge speed from the pressure chamber 13, ascompared to the example described with the aid of FIG. 1. Consequently,the bevel gear 6 can move in axial direction away from the bevel gear 5.

[0067] Another variant is shown in FIG. 13. For this example, thepressure chamber 13 is connected to the suction-in side 72 of pump 20for the discharge. Since this pump has a relatively high capacity forsupplying the pressure medium to maintain the gear unit gearing, acorrespondingly high suction capacity is also available on itssuction-in side 72, thus further increasing the speed for emptying thepressure chamber 13.

[0068]FIG. 13 shows that when reversing the reversing valve 65, thepressure line 17 is simultaneously connected to a return flow line 73.

[0069] All three of the embodiments described with the aid of FIGS. 1,12 and 13 also have in common that the reversing valve 65 must beactivated by the control unit 24 and thus requires a certain expenditurefor the activation. The design according to FIG. 14 is provided as animproved alternative. With this design, the pressure existing in thepressure line 17 is used via the line 75 to activate the control valve65 from one side either counter to or under the effect of an adjustmentspring 74.

[0070] Under normal operating conditions, the pressure exerted by thepressure medium and required for maintaining the gear unit gearing,which must be channeled to the pressure chamber 13, is present in thepressure medium line 17. Under this pressure, the reversing valve 65 isheld in the position shown herein via the line 75 and counter to theeffect of spring 74. In this position, the pressure medium can flow viathe line 17 into the pressure chamber 13.

[0071] However, in case of a gearing adjustment in the gear unit duringthe standstill or the idling, which requires emptying the pressurechamber 13, the control valve 18 position shown in the drawing isrequired, which is preset by the control unit 24 and for which thepressure line 17 is connected to the return flow line 22. As a result,the pressure line 17 practically has no pressure, which also applies tothe line 75, so that the reversing valve 65 consequently can be changedto the alternative position under the effect of spring 74. In theprocess, the pressure chamber 13 is connected to the return flow line67, so that the pressure medium advantageously can flow via a line withlarge cross section back to the pressure medium supply container 21.

[0072] It will be understood that the above description of the presentinvention is susceptible to various modifications, changes andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

What is claimed is:
 1. A bevel gear unit with continuous gearingadjustment and generating of axial contact pressure forces of the bevelgears upon a traction means, rotating between the bevel gears, viatensioning means arranged on the gear unit shafts, which exert forces inaxial direction upon respectively one bevel gear that can be displacedaxially along the respective gear unit shaft, wherein hydraulictensioning means are provided on a first gear unit side for adjustingand maintaining the gear unit gearing and a spring supported tensioningmeans that is braced against a support, fixed relative to the shaft, isprovided on the second gear unit side, wherein an axially fixed bevelgear and an axially movable bevel gear with an extended hub are jointlyarranged on the second gear unit side, the bevel gears are rotationallyconnected and jointly rotate on their gear unit shaft and are coupled tosaid gear unit shaft via a contact pressure mechanism that depends onthe rotational moment or the rotational moment and the gearing, thecontact pressure mechanism consists of a cam sleeve that is fixedlyconnected to the shaft, a cam sleeve formed by the free end of theextended hub and roll bodies for transmitting the force, wherein saidroll bodies are inserted between opposite arranged cam curves and rotatearound the roll body axes extending in radial direction, relative to thegear unit shaft, said roll bodies are guided by rings, are held at amutual distance to each other in the axial center region between the camsleeves with the aid of a spring that is arranged coaxial on theextended hub.
 2. A bevel gear unit according to claim 1, characterizedin that the bevel gears are arranged on a hollow shaft, which ispositioned on the gear unit shaft, such that it can rotate but cannot bedisplaced in axial direction, that the axially fixed bevel gear isrigidly connected to the hollow shaft, that the axially movable bevelgear is connected to the hollow shaft so as to rotate along and that thecam sleeve that is fixedly connected to the shaft is arranged next tothe hollow shaft on the gear unit shaft, such that it can rotate alongand cannot be displaced, at least not in axial direction away from theopposite arranged cam sleeve.
 3. A bevel gear unit according to claim 2,characterized in that the axially fixed bevel gear forms one piece withthe hollow shaft.
 4. A bevel gear unit according to claim 1,characterized in that the roll bodies engage in corresponding recesseson the rings with the aid of pinions that are coaxial to theirrotational axes and project in radial direction relative to the gearunit shaft from the roll bodies.
 5. A bevel gear unit according to claim4, characterized in that a holding ring is arranged in radial directioncoaxial to the gear shaft, either inside or outside of the roll bodies,and that the pinions on the roll bodies are positioned so as to rotateinside holding ring bores, extending in radial direction relative to thegear unit shaft.
 6. A bevel gear unit according to claim 4,characterized in that in radial direction relative to the gear unitshaft, a guide ring in the form of a hollow-cylindrical sleeve isarranged outside of the roll bodies, which guide ring encloses theseroll bodies and the extended hub, that the guide ring can be displacedin axial direction along the extended hub, but is positioned such thatit cannot rotate relative to this hub, that the outward projectingpinions on the roll bodies are positioned such that they can rotate incircumferential slots of the guide ring that extend along a radial planeof the gear unit shaft, which slots have an axial width corresponding tothe diameter of the pinions and are held in the region of the axialcenter between the cam sleeves, that in circumferential direction, thelength of the circumferential slots corresponds to at least half themaximum mutual circumferential path for the cam sleeves of the contactpressure mechanism and that the guide ring end facing the axiallymovable bevel gear is formed as extension onto the spring, such thatmoving in the same direction, it respectively traverses essentially halfthe axial distance traversed by the movable bevel gear.
 7. A bevel gearunit according to claim 6, characterized in that the spring is supportedon one side counter to the axially movable bevel gear and on the otherside counter to the cam sleeve that is fixedly connected to the shaft.8. A bevel gear unit according to claim 6, characterized in that thespring is essentially a disk spring assembly, one half of which isarranged on the hub and the other half on the guide ring, that thespring is supported counter to the cam sleeve via a hollow-cylindricalintermediate segment that encircles the guide ring and that the guidering with radially outward pointing collar on the end is capturedbetween the two halves of the disk spring assembly.
 9. A bevel gear unitaccording to claim 6, characterized in that on the guide ring sectionlocated on the hub, the guide ring is provided with at least one groovethat extends parallel to the axis of the gear unit shaft, in which a pinthat is supported by the hub engages to prevent rotation.
 10. A bevelgear unit according to claim 4, characterized in that outside of theroll bodies and in radial direction relative to the gear unit shaft, aguide ring that encompasses the roll bodies is arranged in the form ofat least one assembly of axially side-by-side arranged, ring-shapedcorrugated springs, having reciprocal undulations in axial directionalong the circumference, that this guide ring is captured in axialdirection between a rotating collar supported by the hub and a collarsupported by the cam sleeve that is fixedly connected to the shaft andis kept axially centered relative to the contact pressure mechanism, andthat radially outward projecting pinions on the roll bodies arepositioned rotating in the axial center of said guide ring.
 11. A bevelgear unit according to claim 10, characterized in that the guide ringconsists of two identical corrugated spring assemblies, arranged axiallyside-by-side, that the corrugated springs of each assembly are bracedagainst each other by means of the undulation peaks that face each otherand are fixedly connected, and that the pinions on the roll bodies arepositioned such that they can rotate between the corrugated springassemblies.
 12. A bevel gear unit according to claim 11, characterizedin that the holding ring is arranged outside of the roll bodies, betweenthese roll bodies and the guide ring of the corrugated springs, and thatthe holding ring is provided with a rotating collar that projects at thecenter radially outward from the holding ring and engages between thecorrugated spring assemblies.
 13. A bevel gear unit according to claim12, characterized in that the bores in the holding ring, which aredesigned to accommodate the pinions on the roll bodies, also extendthrough the collar.
 14. A bevel gear unit according to claim 12,characterized in that the axial width of the collar corresponds to thewidth of the roll body pinions.
 15. A bevel gear unit according to claim10, characterized in that the spring is arranged on the hub and isbraced against the axially movable bevel gear as well as the cam sleevethat is fixedly connected to the shaft with the aid of an essentiallyhollow-cylindrical intermediate segment that encompasses the guide ring.16. A bevel gear unit according to claim 15, characterized in that thecollar supported by the cam sleeve, which is fixed relative to theshaft, and the intermediate segment are combined to form one component.17. A bevel gear unit according to claim 1, wherein the hydraulictensioning means us the associated axially displaceable bevel gear asbottom for a pressure cylinder connected to the bevel gear, whichpressure cylinder forms together with a piston that is fixed relative tothe shaft a pressure chamber to which a pump supplies a pressure medium,taken from a pressure medium supply via a pressure medium supply linefor maintaining and adjusting a gear unit gearing in a manner determinedby a control valve, characterized in that a reversing valve is arrangedinside the pressure medium supply line and that via the reversing valve,the pressure chamber can be connected to the pressure medium supply orthe intake side of a pressure medium pump.
 18. A bevel gear unitaccording to claim 17, characterized in that the reversing valve can beactivated by the control for the control valve.
 19. A bevel gear unitaccording to claim 17, characterized in that the reversing valve can beactivated by the pressure existing inside the pressure medium intakeline.